Poultry is processed, after slaughtering, by scalding to assist in defeathering, defeathering by machine, washing, eviscerating and chilling prior to packing. These treatments are controlled to avoid causing a change in the appearance characteristics of poultry which would make it unsalable.
Poultry, after eviscerating, shows high levels of salmonella bacteria on the surface of the carcass. A large part of carcass contamination with salmonellae can be removed by water washing. While salmonellae can be easily killed by heat, such as during cooking, colony forming units of bacteria can attach and/or reside in the regular and irregular surfaces of the skin, multiply and, thereafter, contaminate working surfaces, hands and utensils. Food spoilage and illness can result from this carryover of bacteria or cross-contamination from the infected carcass to surfaces not heated sufficiently to cause thermal destruction of the bacteria.
Extensive research has been conducted by the art to uncover an economical system for reducing salmonellae contamination of poultry carcasses without causing organoleptic depreciation. Poultry feathers carry large amounts of salmonellae which can contaminate the carcass during scalding. Improper evisceration can also be a source of contamination. The use of acids such as lactic or acetic acid, at levels sufficient to effect bacteriological control, causes organoleptic deterioration of the poultry. At acid levels low enough to avoid organoleptic deterioration of the poultry, bacteriostatic effects are reduced.
A treatment system must be economical, easy to use, compatible with food manufacturing, and not change the organoleptic properties of the poultry. Any change in the appearance of the poultry would make the same unsaleable.
It has been reported that the thermal death rate of salmonellae can be increased during scalding by elevating the pH of the scald water to pH 9.0.+-.0.2. Agents such as sodium hydroxide, potassium hydroxide, sodium carbonate, and trisodium phosphate have been reported as effective pH adjusting agents for use in increasing the thermal death rate of the bacteria. Trisodium phosphate was reported as least effective in increasing the death rate. Sodium hydroxide and potassium hydroxide, while effective bacteriostats, can affect the surface of the carcass adversely. Propionic acid and glutaraldehyde, which were also tried as treating agents, are reported as possibly having unfavorable effects on plucking. See "The Effect of pH Adjustment on the Microbiology of Chicken Scald-tank Water With Particular Reference to the Death Rate of Salmonellae", T. J. Humphrey et al., Journal of Applied Bacteriology 1981, 51, pp. 517-527.
T. J. Humphrey et al. have also reviewed the pH effect of scald water on Salmonella on chicken skin. See "The Influence of Scald Water pH on the Death Rates of Salmonella typhimurium and Other Bacteria Attached to Chicken Skin", Journal of Applied Bacteriology 1984, 57 (2), pp. 355-359. Scald water adjusted to pH 9.+-.0.2 as in the 1981 paper can help to reduce external and internal cross-contamination of carcasses by salmonellas.
The results reported in the first article are based on assays of samples of scald water taken from the scald tank. The article does not show the effect of the agents on bacterial colonies on the surface of the poultry or the organoleptic effect on the poultry meat or skin.
The second paper teaches that pH adjustment of scald water to a pH of 9.+-.0.2 can be used to improve the hygiene of chicken carcasses during plucking by lowering the bacterial carry over from the scald tank.
These references are limited to the scald tank and do not show any long term effect of the agents on the surface of the poultry since the scald water solution and any agents therein are washed off after defeathering.
Humphrey et al. recognize that plucking and subsequent evisceration cause further contamination. The improvements in scalding hygiene reported in their 1984 paper and in their earlier work [1981] help to reduce the growth rate of pathogens on carcass surfaces during plucking but have no measurable effect on the shelf-life of safety of chilled carcasses because of further contamination during evisceration. The organisms responsible for spoilage of meat of this type are added during cold storage or during later stages of processing. (Humphrey et al. 1984 at page 359). Humphrey et al. do not teach reducing the potential for salmonellosis by reducing the incidence and population of salmonella organisms.
Humphrey et al., 1984, also do not show the organoleptic effect of their treatment on the poultry carcasses, much of which is undesirable.
Attempts have been made to pasteurize poultry meat by treating the meat with a solution containing agents such as lactic acid, acetic acid, sodium carbonate, sodium borate, sodium chloride, potassium hydroxide, chlorine and EDTA. All treatments, except sodium borate, sodium chloride, and sodium carbonate, reduced the visual acceptability of the meat. Chlorine failed to destroy bacteria on the surface of the poultry but would be expected to control salmonellae in water. See Chemical Pasturization of Poultry Meat, J. S. Teotia, Dissertation Abstracts Int'l. B., 1974, 34(a), 4142.
It is known that the shelf life of chicken carcasses can be increased 1 to 2 days by chilling the poultry in a solution of 6% sodium tripolyphosphate/0.7% tetrasodium pyrophosphate (Kena-available from Stauffer Chemical Company Division of Rhone-Poulenc, Inc.). See The Antimicrobial Effect of Phosphate With Particular Reference To Food Products, L. L. Hargreaves et al., The British Food Manufacturing Industries Research Association, Scientific and Technical Surveys, No. 76, April 1972, pages 1-20 at page 12. Many patents and articles suggest the use of polyphosphates in preserving meat and fish products.
In addition, it is also stated in the Hargreaves reference at page 7 that G. Pacheco and V. M. Dias in an article entitled Bacteriolytic Action of Phosphates, Mems Institute Oswaldo Cruz, 52 (2) ppg. 405-414, reported on the bacteriolytic action of solutions of monosodium, disodium, trisodium and dipotassium orthophosphates on dead and living cells of Salmonella typhosa, Escherichia coli and Staphylococcus aureus. Trisodium phosphate dodecahydrate is stated to have the greatest lytic action. This reference does not relate to treating poultry.
British patent 935,413 teaches treating raw poultry in the chill tank with a non-cyclic polyphosphate. It is taught that this method provides increased preservation of the poultry flesh by decreasing exudate and thereby decreasing spread of bacteria.
Trisodium phosphate has also been found to be effective in inhibiting the growth of blue mold in cuts and bruises in fruit by treating the broken surface with the solution of trisodium phosphate (U.S. Pat. No. 1,774,310).
The extensive research conducted by the art has been unsuccessful in providing a treatment to reduce salmonellae levels of poultry carcasses without causing extensive organoleptic depreciation.
The invention provides a poultry carcass wash process which removes or reduces existing salmonellae contamination as well as retards further contamination in growth without affecting the organoleptic properties of the poultry carcasses.